The dominant musical genre between the years 2009 and 2012. It combines electronic beats with vocals that are so simple anyone could sing them. To most, this genre sounds like shit. Popular tween wave artists include Rebecca Black, Justin Bieber and, debatably, brokeNCYDE.

Hey, Josephine! Have you heard the new "tween wave" song?
Yeah, it sounds like shit.

Signs you are listening to Tween Wave music: When all you can hear is someone ripping ass into the microphone over a drumbeat. More precisely when it sounds like shit is spilling out of the speakers and puddling on the floor.

"Did you know we're living in the Tween time?... I guess it's the peroid between 2009 and 2012..." - redneck 1

"der I'd heard that." - redneck 2

"So they got this feller down at the bowling alley who gets up on stage and shits his britches.. " - 1

"what fer?" - 2

"I don't know, but he gets up there and strums a geetar and starts loadin' up his britches up like it's goin' out of style... It's like some sort of 'britches holocaust'... he calls it Tween Wave" - 1

A sudden (not very long lasting) phase or trend that kids from the ages about 10-14 are generally interested in. Tween Waves interest people who are in the stage when you are too old for toys but not quite mature for anything else.

Simply: it's popular music from 2009 to 2012. Coined by the creators of South Park in the episode "You're getting old." They are not making fun of a specific band, artist, or anything like that (maybe dubstep would be the best genre to describe tween wave). People are over-thinking this making it seem like they are ripping on Justin Bieber or something, but its a simple definition idiots.

I was just listening to a radio station that plays the most popular new songs, and that tween wave music sounds like total shit!